OK, you all have inspired me. It so happens that I have two 1989 Trek 660's -- my original gray and blue in primo stock condition and another white that has been raced hard but is in good condition and set up as an SS.
Now, the question is, how should I set it up as a CX bike -- SS or geared? DTs or barends? One or two chainrings?
Consider this: '89 660 SSCX. (It was originally gray, like your top one, but now it's been repainted in white appliance enamel).
41x19 ratio. The 19t cog is from an old 9-speed Ultegra cassette. The 17 and 19 are riveted into a single unit and I dremeled off the 17. Then a bunch of 9 and 10-speed spacers gets a pretty precise chain line. The 41t chainring is a Rocket Ring from Harris Cyclery (nice to have a little Sheldon on the bike, RIP).
The brakes are Raleigh branded Mafac knockoff centerpulls. I bought them on eBay a few years ago for a song but never had a bike to put them on. The tires are Kenda Kwick knobbies. They're labeled as 30mm but they look a bit narrower than that to me.
I made some tweaks this morning and took it out for a casual ride with the wife. So far, so good. I think I'll do some dismounting/remounting practice in the park later this afternoon.